Resumo

Proteases hydrolyze the peptide bonds of proteins into peptides and amino acids and have potential application in a wide number of industrial processes, as well as in the structural elucidation and synthesis of proteins. Fungal proteases fungal have an advantage as low material costs, high productivity, faster production and mycelium can be easily removed by filtration. This study aims to produce a protease of fungi from the Brazilian Cerrado. Protease production and nutrient consumption and were analysed, in order to study the pattern of protease secretion by these fungi in different cultivations and its influence in the enzyme activity. It was selected the fungus Aspergillus foetidus and Paecilomyces variotti isolated from Cerrado. To study the effect of agitation on protease production, the cultivation was carried under stationary cultivation and shaker cultivation (150 rpm). These fungi were cultivated for 10 days at 28ºC in medium containing: peptone 2%, Saboraud dextrose broth 3%, yeast extract 2% and skin milk 2%. During this period samples were taken from the broth and an induction curve for this enzyme was built. Protease activity was determined using a solution of azocasein at pH 5.0 as substrate and 37 °C during the whole reaction. One enzymatic unit was defined as the amount of enzyme that produced an increase of 0.001 absorbance units for a reaction in 40 min. Protein concentration was determined by the Bradford method. Reducing sugars were measured by a dinitrosalicylic acid method. When P. variotti was cultivated on stationary condition, protease activity first appeared on the 3^th day (22.3 U/mL), then increased to a maximum value of 40.6 U/mL on the 9^th day with specific activity of 132.4 U/mg. On shaker cultivation, protease production was very low, reaching a maximum value of 7.0 U/mL (specific activity of 16.3U/mg) on the 2^nd day. When A. foetidus was cultivated on stationary condition, protease activity was was very low with a little peak of activity (4.6 U/mL) on 9^th day. When A. foetidus was cultivated on shaker, protease activity was insignificant although, a peak of activity (12.8 U/mL) was found with specific activity of 50.32 U/mg. The analysis of nutrient consumption in all cultures showed that glucose was depleted in 48 h. The pH remained between 4.5 and 6.5 throughout the cultivation time in all cases. Acknowledgement: Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP.